A woman wearing a suit gives testimony in court.

Part 2: Medical Expert Witnesses

Exploring Their Critical Role in Medical Malpractice Litigation

What makes a good expert witness - and what qualities make them credible?

Continued from Part One

What is an Expert Witness’s  Role in Medical Malpractice Litigation?

Legal decisions as far back the 1700s acknowledge that the conduct of medical professionals must be judged by the standards recognized by other professionals in the field. In other words, a plaintiff who accuses a physician of negligently providing care must support his case with testimony from a physician who is critical of the defendant. In the absence of this type of evidence, the plaintiff’s case will be dismissed. The only exception to this requirement are cases where the mistake of the physician is so obvious that no specialized knowledge is necessary to understand that an error occurred. A case where a surgeon amputates the wrong leg is an example of this type of case. No special training is needed to know amputating a healthy leg is an unjustifiable mistake.

Establishing Standard of Care and Causation

Short of an undeniable mistake, expert testimony is required in medical malpractice cases for two different but related issues, the standard of care and causation.

1. Standard of Care

On the first issue, expert witnesses provide the testimony that is used to inform the jury what the defendant in the case should have done in response to the specific facts presented. Once the standard of care is established, the expert can offer their opinion on whether the actions of the defendant-health care professional were consistent with what a similarly situated, reasonable professional would do. Obviously, the issue of what the standard of care required is crucial to malpractice litigation. If the jury believes the defendant-health care provider acted in compliance with the standard of care, the defendant will win the case. Irrespective of how severe a plaintiff’s injury may be, if a care provider acted reasonably, the plaintiff in the case cannot prevail.

2. Causation

Second, the testimony of an expert witness may also be necessary to establish that the plaintiff’s claimed injury was caused by the conduct of the defendant. Even if a healthcare provider acted outside of what the standard of care required, and the patient suffered an injury, the plaintiff must establish a causal link between the breach and the injury in order to prevail at trial.

This issue is frequently the source of disputes in malpractice litigation, particularly in cases involving an allegation of a delayed diagnosis. For instance, if a plaintiff is claiming that a delay in making a cancer diagnosis led to an adverse outcome, the plaintiff must provide expert testimony to establish that the patient’s course would have been different with an earlier diagnosis. The competing expert opinions in this type of case will involve differing opinions as to the interplay between the efficacy, timing, and availability of various treatments.

The Jury

Typically, both the defendant and the plaintiff in a malpractice case will present testimony from retained experts. This often leaves the jury to pick from competing versions of what the standard of care required, whether the defendant’s conduct met that standard, and/or whether the conduct at issue was the cause of the plaintiff’s claimed injuries. Usually, the jury’s determination as to which of the experts presented the most credible testimony will dictate which party will prevail.

What Qualities Make an Expert Witness Successful?

The role of expert witnesses in malpractice litigation is not limited to offering testimony at trial. In fact, one of the most critical functions of experts happens long before trial. When a patient suffers an adverse outcome and begins the process of pursuing a legal claim, lawyers for the healthcare professional and the patient will undertake separate investigations of the merits of the potential lawsuit. In this investigation, the attorneys involved will ask experts in the relevant field to review the available records. After this review, the lawyer will consult with the expert for a preliminary opinion on whether a viable claim exists based on the circumstances of the patient’s care. This initial expert consultation is crucial for accurately advising clients on whether the treatment at issue may give rise to legal liability or whether a claim is defensible. While early expert reviews are useful, in the event a case proceeds to a trial, a jury of lay persons will ultimately decide if a defendant is liable for a plaintiff’s injuries. In making this determination, the jury will decide which party’s expert presented a credible opinion on the issues in the case.

However, before determining if an opinion is credible, the jury must understand the substance of the expert’s testimony. Thus, the hallmark of a great expert witness is the ability to explain complex medical issues in a way that makes sense to persons without medical training. An expert with sterling qualifications and an unassailable understanding of the issues in a case may perform poorly at trial if she is unable to translate the medical issues into language an ordinary person can understand. An effective expert can assume the role of a teacher who leads the jury to the desired conclusion by presenting a comprehensible and cohesive explanation of the issues. The very best experts are able to hold the attention of jurors even when discussing technical concepts through engaging explanations and helpful analogies.

What Issues Impact the Credibility of an Expert Witness?


If both parties present understandable explanations of why they believe they should win the case, the jury will necessarily be forced to determine which of the experts was most believable. As such, it is crucial that expert witnesses avoid the appearance of bias. This reality is the reason why healthcare professionals accused of malpractice nearly always enlist the assistance of an outside expert to help make their case. A juror may assume that a doctor accused of malpractice will give self-serving testimony when accused of wrongdoing. However, the use of hired experts can create its own set of challenges to earning the trust of a jury.

The "Hired Gun"

At trial, attorneys may try to undercut the credibility of an expert witness by painting an expert as a “hired gun,” willing to say anything for the right price. Because both parties will likely be using hired experts, this type of attack on a witness’s credibility can be a dual-edged sword. However, there are circumstances that can effectively create questions in the mind of a jury concerning the reliability of an expert’s opinion. For instance, the impartiality of an expert witness can be questioned if the expert reviews cases exclusively for one type of litigant, either plaintiffs or defendants. If during a cross-examination an expert witness is forced to admit that he has been hired by the same plaintiff’s attorney multiple times and has offered opinions critical of care providers every time he has been called to testify, the jury may be inclined to doubt the opinions provided. The jury may assume that the expert will say anything the plaintiff’s attorney wants so that the expert continues to be hired in the future. By contrast, if an expert can testify that he is regularly retained by both plaintiff and defense attorney to review cases, concerns of bias against one type of litigant are obviated.


Ultimately, the use of expert testimony heavily impacts whether a party wins or loses a medical malpractice claim. Retaining an expert with the wrong type of qualifications, or an expert whose credibility can be called into question may decide the outcome of a case long before the trial even begins. Even before a case is filed, an unreliable opinion from an early expert review can have a disastrous effect on a case. As such, attorneys and parties involved in medical malpractice litigation must carefully consider all options when making decisions related to retaining an expert as part of a case strategy. 

About the Authors

Acacia Brush Perko

Acacia Brush Perko

Acacia is a shareholder with Reminger Co., L.P.A. who practices in both Ohio and Pennsylvania. Acacia has devoted her legal career to representing health care professionals and institutions and is proud to do so. She has extensive experience in complex medical malpractice and long-term care matters. She has successfully represented physicians, nurses, hospitals and long-term care facilities in state and federal courts.

Kenton H. Steele

Kenton H. Steele

Kenton is based in Reminger Co., LPA's Columbus office, and actively practices throughout Ohio and West Virginia. His practice is focused on matters involving professional liability, including medical malpractice, long-term care and insurance professionals. Kenton has also written and spoken extensively on the intersection of law and advancing technologies.

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